Short and sweet guys, which is better? Trying to improve my 60ft. times.

 

You don't want your suspension to bottom out. Soft in front, stiff in back.

 

I'm sure there's probably a happy medium between too much squat, and none at all. To the best of my knowledge, I'd say the best would be to use 90/10 drag shocks in the front to let it lift quickly and easily, but IMO, you'd want soft(er?) shocks in the back to let it squat a little? I know that for the most part, you want the car to be "tight" --- ie: the fewer rubber mounts and bushings, the better --- so that the power isn't lost to these parts, but I still think you need a certain amount of weight transfer to get the best traction as well.

I get 2.0 - 2.1 60' times though................so you probably shouldn't take advice from me!!

 

anti squat

 

You may do better in the Drag Racing forum with your question. But so far, the answers are off base, IMHO. I am not a suspension guru by any means. But squat and anti-squat have nothing directly to do with shocks and springs. They are characteristics of the suspension geometry. Increasing rear anti-squat plants the rear tires when accelerating and results in better traction. On a torque arm suspension like a 4th gen's, the most practical way to add antisquat is lowering the rear attachment point of the LCA's (relocation brackets). The length and design of the torque arm also is supposed tohave an influence, though I am not sure quite how that works.

What springs and shocks do is aid (or inhibit) weight transfer, which is separate from squat. To maximize drag strip traction, you want to promote weight transfer to the rear wheels. Removing (or softening) the front sway bar, using front shocks with low rebound damping, lower rear spring rate, etc. all contribute to weight transfer. Obviously, more weight transfer is better (for drag racing).

I am not too good at explaining this, like I said, the Drag Racing forum may be better. Also, people with suspension knowledge seem to hang out in the Autocross/Road Racing forum more than anywhere else.

Rich Krause

 

Listen to Rich Krause. He's correct.

Acceleration transfers weight from the front to the rear because the force propelling the car is the thrust force at the rear tire contact point, and the resistance to acceleration (the vehicle mass) has it's center above the ground, about 21-23 inches. That's a moment arm, and the longer the arm the more force (weight) is transferred. Now if you let the front end rise with loose rebound (90/10) front shocks, you are raising the height of the center of mass (center of gravity), which increases the weight transfer to the rear.

The normal reaction of a rear suspension when weight is added, either from a load in the trunk or acceleration, is to compress or "squat". As Rich said, a suspension with anti-squat designed into it uses the reaction from the tires on the pavement to push up on the rear of the body (sprung mass). So if something is pushing the rear end up, there is an equal and opposite reaction back down into the axle and unsprung stuff like the tires, so the tires have more downward load. It sounds like voodoo, but it's just physics. Think of a bottle jack placed inside the rear spring; if you pump it up it pushes the body up and the axle down.

If there was 100% anti-squat designed into the rear suspension, the rear of the body would remain level during any acceleration. With more than 100% anti-squat, the rear end will lift under acceleration. This happens in some drag cars. Some leaf spring Mopars exhibit this rear lift during shifts at the strip. Watch the rear tire gap change.

On the other hand, if the rear squats (body drops) it is lowering the center of gravity which reduces the weight transfer. This is the opposite of what you want to launch quicker.

So by letting the front rise at launch, and also having significant anti-squat designed into the rear suspension geometry, vertical load on the rear tires is increased, and 60 ft times should improve.

My $.02

 

You can have too much anti-squat also. I've been there with my 4th gen. I was running the LCA's in the bottom hole for a while. This gave me so much antisquat that under slow motion video I could see that it was pounding the tires so hard that they would rebound and unload. I moved the LCA's up 1 hole in the back, and life was good!

Steve

 

Thanks guys.

 

Good point. What you got was power hop, IMO. Lowering the rear mount of the LCA increases the anti-squat but sometimes a side effect is power hop or axle hop. Your solution was good.

With some work on shock damping, bushings, and maybe tires you might be able to eliminate the hop with the increased anti-squat, but that's a lot of effort. More bite = more chances for problems, or "There's no free lunch."